This invention relates to coin detection and validation means, and particularly to coin detection and validation means for distinguishing between good and bad coins deposited in coin-operated vending systems. The subject means include a novel controllable tank type ringing circuit.
Throughout this application the term "coin" is used to mean any coin (whether valid or counterfeit), token, slug, washer, or other metallic object or item, and especially any metallic object or item which might be used in an attempt to operate or to cheat a coin-operated device or system. A "valid coin" is considered to be an authentic coin, token, or the like, and especially an authentic coin of a monetary system or systems in which or with which a coin-operated device or system is intended to operate and of a denomination which such coin-operated device or system is intended selectively to receive and to treat as an item of value.
A number of coin detection and validation means, designed in accordance with various coin handling systems, have been constructed and used in various vending applications. Most of the known coin detection and validation means are mechanical in construction and are designed to validate coins on the basis of their physical shapes or sizes. In more recent years, coin validation means have included electromechanical and electronic validation devices which operate to validate coins on the basis of the physical shape and size of coins. Still, other electronic coin validation means determine the validity of coins by determining the metallic content thereof as by using inductive means or coils.
Included among such coin validation means are devices such as those disclosed in U.S. Pat. Nos. 3,780,137; 3,918,563; 3,918,564; 3,918,565; 3,918,851; 3,966,034; and 4,151,904, all of which employ inductors of known characteristics as part of an oscillator or tank circuit In such devices, the inductor is so positioned as to have its field affected by the presence of a coin in the field thereof which causes a change to occur in an oscillator or like output. Such changes have been used as a basis for detecting and distinguishing between different coins of the same or of different denominations and coins having different characteristics. Generally, such devices operate when a coin is present in the field of the inductor to produce a measured or derived value representative of such coin, and thereafter such value is used to operate in various ways means that compare such measured or derived value against different predetermined values to determine whether or not such coin is valid or genuine. For the most part, the greater the number of different predetermined values against which the measured or derived value is compared, the more circuitry and especially replicative circuitry is required by the coin validation means. To some extent it has been possible to reduce the amount of replicative circuitry through the use of a programmable memory such as described in U.S. Pat. No. 3,918,565. This patent teaches the construction of coin validation means that include a programmable memory for storing a plurality of different predetermined values, and includes comparison means to compare the measured or derived values representative of the coin undergoing examination against the plurality of stored predetermined values to determine whether the coin is a valid coin.
More recently, as disclosed in U.S. Pat. Nos. 4,254,857; 4,460,003; 4,625,852; and 4,739,869, it is known to use ringing circuits advantageously in coin detection and validation means of coin-operated systems U.S. Pat. No. 4,254,857 discloses a tank circuit that is electrically shocked to produce a damped wave signal which will be altered by the presence of a coin in the field of the tank circuit The altered damped wave signal then becomes a signature unique to the metallic content of the particular coin being examined The damped wave output signals produced by such devices have certain distinctive characteristics such as distinctive magnitude, frequency, and/or the shape of signal envelope
The devices disclosed in U.S. Pat. Nos. 4,625,852 and 4,739,869 employ two pairs of coils which are pulsed separately to produce a ringing damped wave signal from each coil pair. One coil pair is connected in a series opposition polarity arrangement and the other coil pair is connected in a series aiding polarity arrangement. The coil pair connected in the series aiding polarity arrangement provides good discrimination between certain metals that are relatively close in resistivity, and can thus readily discriminate between certain coins on this basis. However, discriminating between certain other coins with values of resistivity that are close to one another is more effectively realized by use of coil pairs where the coils are connected in a series opposition polarity arrangement.
U.S. Pat. No. 4,432,447 discloses a coil pair which is connected in a transformer relationship to transmit a signal from a primary coil to a secondary coil when a coin being examined passes between the two coils. The passing of the coin between the two coils changes the mutual inductance between the coils. The resultant change in the secondary signal from the secondary coil represents a particular resistivity value associated with the coin This particular resistivity value can then be used to determine whether the coin is a valid coin.
U.S. Pat. No. 4,091,908 discloses a detector circuit that uses two transformers having signals applied to their respective primary windings, each having a pair of secondaries connected in series opposition The resultant signals across the coil pairs are monitored and used to indicate the extent to which the mutual conductance of the transformers is affected by the resistivity of the coin as it passes through the magnetic flux paths of the transformers.
U.S. Pat. No. 4,353,453 shows a coil pair connected in a series aiding polarity relationship, with a capacitor connected across the pair. In this construction the coin passes between the coil pair to cause a change in the mutual conductance. The resultant change in the output signal across the coil pair is related to the resistivity of the coin passing therebetween. The output signal is used to determine the particular coin characteristic desired.
Other known coin detection and validation circuits are disclosed in U.S. Pat. Nos. 4,436,196, 4,574,935, and 4,492,296. U.S. Pat. No. 4,436,196 shows two transformers having their primaries connected in a series aiding arrangement and a single secondary winding connected in a series opposition arrangement. The passing of a coin between the primaries and the secondary causes a change in the output signal from the secondary winding. This signal is utilized to discriminate between coins and slugs having different resistivities. In U.S. Pat. No. 4,574,935, a first tank circuit is pulsed simultaneously with a second tank circuit which is tuned to some desired frequency. The validity of a coin passing between the two tank circuits is determined when the output signals from the two tank circuits are equal. U.S. Pat. No. 4,492,296 discloses a construction having two coils between which a coin passes. The coils are part of an oscillator circuit which is shown connected in a series aiding polarity arrangement used to discriminate between coins having various resistivities
The present invention is an advancement over the coin detection and validation means disclosed in the above mentioned patents that employ pulsed inductive circuits and those that have series connected inductor pairs. The present invention is designed to operate a ringing circuit that has a pair of series connected inductors, each having its own associated capacitor, and each of which is rung independently of the other. The frequency of the damped wave output of each inductor-capacitor tank circuit is established by the value of the capacitor associated therewith. A coin passing between the two series connected inductors causes a unique damped wave pattern to be produced which is indicative of the resistivity of the coin. The feature of having two pairs of coils, as shown in U.S. Pat. No. 4,625,852, one of which is connected in a series aiding polarity arrangement and the other of which is connected in a series opposition polarity arrangement, is accomplished in the present invention using a single pair of inductors.
Many new forms of coin detection and validation means are shown in this specification including those which use two LC tank circuits connected in series or in parallel using one or seperate pulsing means to produce damped waves when energy stored by a charging pulse is removed. The tank circuits or the coils therefor can be located on opposite sides of the coin path and in some cases on the same side. The coils in the tank circuits can be air coils or coils in associatied with ferrite pot cores, and the seperate tank circuits, each of which has its own discrete capacitor can have the same or different resonant frequencies and they can be charged by the same charging pulse or by different charging pulses of the same or different frequency and/or of the same or different phase.
The present invention provides a method of maintaining the selectivity of coins throughout the variance of component or environmental changes One such method is shown in U.S. Pat. No. 4,546,869 whereby the stored values of the acceptability ranges are used to compare measured values of coins tested, and are modified as conditions for testing change U.S. Pat. No. 4,538,719 in column 15, lines 50-55 shows the means to vary the input driving signal to the inductor from initally programmed coin criteria. The coin criteria for selectively varying the input driving signal can be altered as conditions for testing change.
The present invention provides automatic refinement of coin selectivity in a different manner than the aforementioned patents. It does not compare a resultant test signal measurement to that stored in a memory as in U.S. Pat. No, 4,546,869, and it does not change the stored criteria for a driving signal characteristic as in the U.S. Pat. No. 4,538,719. The present invention accomplishes automatic maintenance of coin selectivity by modifying the stored data which controls the proportioning of the resultant test signal before it is compared to a fixed voltage level.
A principal object of the present inventon is to provide improved means for detecting and validating coins and other metallic objects.
A further object is to provide an improved coin validation means that utilizes two ringing circuits.
Another object is to provide coin validation means that can be used to distinguish between a number of different denomination coins without the need for replicative circuitry.
Another object is to provide electronic coin validation means that can be used to distinguish between coins of differing denomination without the necessity of changing any characteristics of a driving signal applied to the inductive means.
A still further object of the present invention is to provide a coin validation means that utilizes a microprocessor to control the operation of a variably controllable resultant test signal proportioning means.
An object of this invention is to provide automatic compensation for any changes in circuit components or coin population.
Another object is to provide an electronic coin validation means that is readily usable with other coin validation means.